This invention relates to glasses provided with specific coatings which may thereafter be heat treated at temperatures sufficiently elevated to bend, heat-strengthen, and/or temper the glass. The invention finds particular utility in architectural and automotive glass production.
The popularity of metal or metal-oxide coated glasses in architectural and automotive design is well known. As reported prolifically in patent and other literature, such glasses thru the manipulation of the coating's layering system, usually by choice of metals and/or metal oxides and/or thicknesses, can usually achieve, quite acceptably, the degree of reflectance, transmittance, emissivity and durability, as well as the color, desired. See, for example, U.S. Pat. Nos. 3,935,351; 4,413,877; 4,462,883; 3,826,728; 3,681,042; 3,798,146; and 4,594,137 just to name a few.
It has also been well reported that while several reasonably acceptable techniques exist for applying such coatings, one of the most efficacious, and thus preferred, is the well known technique referred to as "magnetically enhanced sputter-coating". Such a technique is reported in U.S. Pat. No. 4,166,018, a recognized fundamental teaching on the subject. (See also, Munz et al. "Performance and Sputtering Criteria of Modern Architectural Glass Coatings" SPIE Vol. 325 Optical Thin Films, 1982, pg. 65-73.) While efficacious, for many known layer systems its use may result in mechanical durability being less than that achieved by another known method called the "pyrolytic" technique. As a reverse function, however, sputter-coated systems often achieve better infrared reflectance than typical pyrolytic coatings.
Because of the popularity of these coated glasses, numerous companies have entered the marketplace in recent years. Some of these glasses are sputter-coated. Others are coated by other techniques such as the pyrolytic process. Some are bent, others are flat. While the precise compositions of many of these coated glasses is not known, what is known is that none of them achieve the same characteristics of this invention, nor do they appear to employ the same unique combination of elements that achieve these characteristics, and thus make up the subject invention.
For example, one system that is generally known is the Leybold "Spectrum" windshield glass system known as TCC-2000. In this system four or five layers of metals and metal oxides are employed to obtain a sputter-coated glass which, being somewhat heat treatable at temperatures up to 1100.degree. F., may be used as a pre-coated glass for making bent or unbent, glass windshields, provided rather rapid time limits are placed on the heat treatment. The layering from glass substrate outwardly usually includes a first layer of tin oxide, a second layer of a nickel/chromium alloy (usually about 80/20), a third layer of silver, a fourth layer of the nickel/chromium alloy, and a fifth layer of tin oxide. In addition to the rather low upper limit on heat treatment temperatures and times, the resultant coatings are rather soft and exhibit such unacceptably low chemical resistance characteristics that they can realistically be used only on the inner surfaces of laminated glass windshields. Leybold's other systems, such as its "Solar coatings" (sputter-coated SnO.sub.2 /Cr/SnO.sub.2); "Low-E" (sputter-coated SnO.sub.2 /Ag/Al/SnO.sub.2); and "Revised Architectural" (sputter-coated SnO.sub.2 /Ag/NiCr/SnO.sub.2, NiCr being 80/20) have not proven to be heat treatable.
Exemplifying further knowledge prior to the subject invention, are several systems (in the patents, as well as those marketed) which recognize that various oxides such as titanium dioxide, tin oxide, mixtures of tin oxide with other metal oxides (e.g. with ZnO) may be used as an efficacious overcoat or undercoat for durability and other properties. In addition, several recognize that aluminum, nickel and a wide variety of nickel-based alloys such as stainless steel (i.e. less than about 15% Ni), Inconel, etc., may be used as efficacious intermediate layers in sputter-coated glasses. Exemplary of these types of glasses include the following:
__________________________________________________________________________ Layer System Company Trade Designation (on Information and Belief) __________________________________________________________________________ PPG Solarcool single layer, heat treatable, non-sputter coated, Cr.sub.2 O.sub.3 Solarban stainless steel bearing, not heat treatable, sputter-coated, various oxides, nitrides and metals Sungate 100 sputter-coated, not known to be heat treatable (SnZn)O.sub.2 --Ag--Ti--(SnZn)O.sub.2 TiO.sub.2 Ford Sunglass Reflective similar to PPG Solarcool single layer, unknown oxide Sunglass Hp Reflective similar to Solarban SPI Sunglass HP Reflective similar to Solarban Sunglass HR sputter-coated, not known to be heat-treatable, oxide-Ag-Metal-Oxide LOF Eclipse pyrolitic, heat treatable, not sputter-coated AIRCO Solar Coatings numerous sputter coatings of various oxides, nitrides and metals, in- cluding stainless steel (e.g. less than 15% Ni), none are heat treatable Architectural L.E. sputter-coated, not known and to be heat treatable Sunbelt L.E. ##STR1## Aircool 72 & 76 sputter-coated, non- durable, not known to be heat treatable ZnO/Ag/Zn/ZnO/Ag/Zn/znO.sub.x Airco Super-H SnO.sub.x /Al/Ag/Al/SnO.sub.x (Heat Treatable) sputter-coated, non- experimental durable, heat treatable LEYBOLD Solar coatings sputter-coated, not heat treatable SnO.sub.x --CrN--SnO.sub.x Low-E sputter-coated, not known to be heat treatable SnO.sub.x --Ag--Al--SnO.sub.x Revised Architectural sputter-coated, not known to be heat treatable SnO.sub.x --Ag--NiCr--SnO.sub.x (Ni/Cr is 80/20) TCC-2000 discussed above. Heat treatable but not durable (Ni/Cr is 80/20) SnO.sub.x --NiCr--Ag--NiCr--SnO.sub.x GLAVERBEL StopSol single layer of unknown metallic oxides, heat treatable pyrolytic coating Prestige sputter coatings of oxide-Ag-oxide, oxides unknown, not heat treatable or durable Comfort single layer of unknown metal oxide, heat treatable pyrolytic system PILKINGTON Reflecta Float single layer of metallic oxide (possibly Cr or Ni containing) heat treatable pyrolytic, not sputter-coated Sputtered coatings various layers of oxides, nitrides and metal, metal can be Ni bearing of 15% or less Ni, not heat treatable ASAHI (experimental) heat treatable, total Sunroof coating constituents unknown, may have some Ni, most probably Ti and Al GUARDIAN "S", "T", "C" series various sputter-coated, (Luxguard) RP-20, Nu-52, LE-75, non-heat treatable Appln. S. N. 077.226 layer systems of oxides filed 7/24/87 and and/or metals. Oxides now U.S. Pat. include SnO.sub.x, ZnO.sub.x, TiO.sub.2 No. 4883721 and the like as protec- tive coatings. Typical metals are Cu, Ag, stain- less steel (less than 15% Ni) and/or Ti. LE-75, for example, has included in the past in one embodi- ment an SnO.sub.x --Cu--SnO.sub.x layer system which is not heat treatable. Modern LE-75 layers are more complex systems involving TiO.sub.2, ZnO.sub.2 and other non-nickel bearing metals. FLACHGLASS Sightchrom (INSnO.sub.x)/Pt/(INSnO.sub.x) (also St. Gobain) heat treatable cost prohibitive scratches U.S. Pat. Nos. various layers with 3,901,997;4,497,700 Ag,Au or Cu coating and 3,978,273 including 80/20 Ni/Cr Infrastop sputter-coated, not heat treatable, various layers of oxides, nitrides and metals, some metals may contain 15% or less Ni U.S. Pat. No. metal silicide coating 4,816,054 sputter-coated and said to be heat treatable __________________________________________________________________________
(In the above listing tin oxide is indicated as SnO.sub.x. At times in the prior art it is stated as SnO.sub.2. No distinction is drawn herein between these two forms of reference for tin oxide.)
Of these glasses, perhaps three may be classified as coming closest to the subject invention; namely, TCC-2000, Airco Super-H experimental and Sightchrom. TCC-2000's lack of durability and its drawbacks are discussed above. Sightchrom employs an indium-tin oxide combination as its first and third of three coatings. As its intermediate metallic layer it employs platinum. It scratches easily and it is prohibitive cost-wise. Airco Super-H experimental, while heat treatable, employs silver, and has been found to lack durability.
None of these listed glasses achieves or recognizes the particularly unique results that are obtained when only tin oxide is used as an overcoat (and also optionally as an undercoat as well) alone or with aluminum, together with nickel or a specific type of nickel alloy in a sputter-coating process, as contemplated by this invention, to produce unique heat treatable glasses with excellent tolerance to temperatures above 1100.degree. F. at times usually employed in non-coated glass heat treatments, and which in preferred embodiments are not only heat treatable, but durable (scratch resistant) as well. Such glasses, in fact, are so durable that there is no need to laminate them to protect the layer system from ordinary use.
U.S. Pat. No. 4,790,922 exemplifies the efficacy of the subject invention. This patent discusses the difficulties which the prior art has experienced in attempting to develop coated glasses for architectural and automotive purposes which must be, or are desirably, put through their heat treatment step (e.g. tempering, bending, or both) after the coating is applied. The solution posed in this prior art patent is a rather complex layer system consisting of a first layer of an Sn/Zn oxide, a second layer of titanium, a third layer of silver or stainless steel, a fourth layer of titanium, a fifth layer of an Sn/Zn oxide, and a sixth, top layer of titanium oxide. The patent, while stating the material is heat treatable, acknowledges in Col. 4, line 56-57, that: "The glass can then be heated to approximately 1100 degrees fahrenheit . . . " In addition to being a rather complex system, it relies upon titanium for three of its layers, and indeed its effectiveness. Titanium, experience shows, is a difficult (slow) element to sputter. By teaching the need to overcoat the Zn/Sn oxide fifth layer with TiO.sub.2, there is a teaching away from the subject invention which unexpectedly has found that when tin oxide is used alone or with aluminum, together with certain select nickel compounds, it overcomes the problems in this patented system, and there is, among other advantages, no need for a TiO.sub.2 overcoat.
There are three different types of heat treatments that are generally employed to work glass for architectural or automotive purposes; namely, bending, tempering, and a lesser form of tempering called "heat strengthening". When bending without tempering conventional 1/4" clear float glass, for example, times of 10-30 minutes at 1150.degree. F. or more are generally necessary to use. In heat strengthening or tempering such glass, with or without bending, temperatures as high as 1450.degree. F. (e.g. 1150.degree.-1450.degree. F.) are normally employed for about 2-5 minutes. As can be seen, there are significant drawbacks to the known or reported prior art techniques for providing heat treatable coated glass, particularly of the efficacious sputter-coated type.
Coated glasses for use in architectural or automotive design generally have eight (8) characteristics which determine their efficacy and/or marketability: commercial feasibility, durability (mechanical resistance to abrasion), chemical resistance, long-term stability, emissivity, transmittance, reflectivity and color. In prior systems, some of the characteristics had to be significantly impaired in order to achieve the necessary degree of acceptability for the remaining characteristics. For this and other reasons, therefore, it is apparent that there exists a need in the art for a heat treatable, coated glass useful in architectural and/or automotive design which does not unduly sacrifice the above eight (8) characteristics, and preferably, which also may be heat treated (i.e. bent, tempered, and/or heat-strengthened) at the upper temperature ranges and times of such treatments. There is also a need for such a coating to be formed by sputter-coating techniques, but which does not sacrifice mechanical durability as compared to pyrolytically formed coatings.
It is a purpose of this invention to fulfill the above-described needs, as well as other needs apparent to the skilled artisan from the following detailed description of this invention.